1. Field of the Invention
This invention relates, in general, to vehicle safety apparatus and, more specifically to vehicle safety apparatus for locating an object surrounding a moving vehicle and to provide an indication of the vehicle's capability of stopping to avoid collision with the detected object.
2. State of the Art
Radar systems for controlling a vehicle in response to the detection of an object surrounding the vehicle are known. U.S. Pat. No. 3,898,652 discloses such a vehicle radar system in which front, rear and side sensors are mounted on a vehicle. A radar means is connected to each of the sensors and calculates the distance and closing speed to an object detected by one of the sensors, particularly the front or rear sensors. The vehicle velocity is used to calculate a distance which, under existing conditions, is the minimum safe distance the vehicle should be with respect to the detected object if the detected object immediately stops, so as to provide an indication of the moving vehicle's capability of stopping without collision with the detected object.
The radar system provides an indication to the operator of the vehicle of the vehicle's capability of stopping prior to collision with the detected object. The indicator is preferably a visual indicator in the form of a light on a display console mounted in the vehicle. This radar system also provides for automatic control of the vehicle accelerator and/or brakes to automatically slow the vehicle down to avoid collision an with object detected in front or to the rear of the vehicle.
The existing road conditions, whether wet, dry or icy, is also a factor in the computation of the safe operating distance of the vehicle and is input to the radar control apparatus via a switch mounted on the operator console.
The radar employed for the front and rear sensors in this system is a Doppler radar. While the vehicle safety and protection system disclosed in this patent is effective in detecting and controlling the vehicle within safe operating limits to avoid a collision with a detected object, it has been found that certain improvements could be made to this system to improve its efficiency and to provide greater operator control over the system.
The Doppler radar employed in this patented system is large and requires a considerable amount of space in the vehicle. The large diameter radar and low operating frequencies is necessary to provide the desired narrow beam directly in front of or to the rear of the vehicle so as to avoid detecting objects to the sides of the vehicle which do not prevent a potential collision situation to the vehicle. Specifically, the radar in this patent as well as other similar prior art vehicle radar systems has an effective diameter of six inches at an operating frequency of 10 to 24 GHz. This effective diameter and operating frequency creates a radar beam having a 6.degree. beam width which is particularly suited for vehicle applications as 6.degree. covers one road lane width at the range of the radar. However, the six-inch diameter radar is large and unwieldy and cannot easily be mounted in existing vehicles due to minimal available space at the front and/or rear of such vehicles. However, merely employing a smaller effective diameter radar at a higher operating frequency, such as 24 GHz, has the effect of increasing the beam width to approximately 18.degree.. This is unsuitable for vehicle applications as 18.degree. would cover up to three lanes of roadway and thereby detect objects to the sides of the vehicle in front or back of the vehicle which do not pose a potential collision situation.
Thus, it would be desirable to provide a vehicle radar safety system which is capable of employing a smaller diameter radar than that previously employed in vehicle radar systems. It would also be desirable to provide such a small diameter radar in a vehicle radar system which is capable of operating at a high frequency and yet provides a sufficiently narrow radar beam. It would also be desirable to provide a vehicle radar safety apparatus which enables the operator of the vehicle to selectively control various operating features of the radar system. Finally, it would be desirable to provide a vehicle radar system which automatically compensates for existing road conditions, i.e., wet or dry.